1. Field of the Invention
The present invention relates to a semiconductor module and a motorized equipment having a controller, which includes the semiconductor module and which is arranged on one axial side of a shaft of an electric motor.
2. Description of Related Art
Conventionally, an electric power steering system for assisting steering, which is performed by a driver, has been publicly known. Generally, an inverter circuit for producing an alternating-current power from a direct-current power is used in a controller that controls drive of an electric motor in the electric power steering system. The inverter circuit is constructed by mounting electronic components such as semiconductor devices such as transistors, resistors and capacitors on a substrate. For example, Patent document 1 (JP-A-2005-212722) describes a power substrate that is applied to an electric power steering controller and that is mounted with semiconductor switching devices and the like.
In the conventional technology described in Patent document 1, a heat sink is provided to be in surface-to-surface contact with the power substrate. A heat generated by large-current components and wiring patterns on the power substrate is dissipated through the heat sink. The entire power substrate is in contact with the heat sink. Therefore, heat dissipation of elements having relatively high cooling priorities and heat dissipation of elements having relatively low cooling priorities are performed substantially equally. Therefore, if it is aimed to achieve a sufficient effect of the heat dissipation from the elements having the relatively high cooling priorities, there occurs a problem that a body size of the heat sink enlarges and weight of the heat sink increases. The cooling priority means a degree of necessity for cooling.